It is well known in the prior art to use an apparatus which frictionally engages a human thigh and calf to prohibit abnormal lateral, fore and aft motion of these body members, avoiding improper stresses on the knee. In particular, U.S. Pat. No. 2,144,641, to Snyder, provides a knee brace which frictionally engages both the thigh and calf and has a pair of flattened vertical support shafts journaled by a rivet, where the shafts prohibit abnormal lateral, fore and aft motion of the knee. These devices are useful where the user's knee has been previously injured, protecting the knee from further injury and permitting continued activity while the knee joint is healing.
The prior art also contemplates the use of knee pads to both protect the knee and give support to it, giving greater support when the knee is bent. In particular, U.S. Pat. No. 3,965,486, to Lightbody, discloses a pneumatic knee pad having two chambers and a multiplicity of hollow fingers communicating with the chambers. When the knee is bent, the air in one or both of the chambers is forced into one or more of the fingers which tighten against the knee prohibiting separation of the various bones of the knee and reducing the risk of torn ligaments, tendons, and cartilage.
The prior art also discloses a pair of fluid filled chambers positioned on the thigh and calf adjacent the knee joint and fluidly connected so as to permit fluid migration from one side of the device to the other upon application of an external force to the knee. These devices are principally used to protect the user's knee from injuries during athletic contests while permitting free use of the leg. Upon the application of an external force, such as contact during an athletic competition, a lateral force to the knee causes fluid to migrate from the engaged side of the knee to the opposite side causing expansion of the fluid filled chamber on the opposite side. By increasing fluid pressure on the side opposite that of impact, the knee is better braced, thereby reducing the possibility of injury to the knee joint.
Although these prior art devices provide some support to the knee joint, they have failed to provide control support in conjunction with and as a result of flexure of the knee. Further, the devices have failed to provide adequate support to the knee joint without resulting in overly restricting movement of the knee. Thus, a need exists for a knee brace which provides controlled lateral support at defined points of knee flexure without restricting movement of the knee joint.